$ docker build -t dockly .
Sending build context to Docker daemon  16.52MB
Step 1/9 : FROM node:8-alpine
Get https://registry-1.docker.io/v2/library/node/manifests/8-alpine: unauthorized: incorrect username or password
$ docker login
Authenticating with existing credentials...
Stored credentials invalid or expired
Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.
Username (XXXXXX): <XXXXXX>
WARNING! Your password will be stored unencrypted in /root/.docker/config.json.
Configure a credential helper to remove this warning. See
https://docs.docker.com/engine/reference/commandline/login/#credentials-store
Login Succeeded